1. Field
The present embodiments relate to a bonding structure of a substrate and a component and to a method of manufacturing the same.
2. Related Art
In the related art, when an electronic component and an electrode formed on a substrate are bonded to each other by using solder, for example, Sn—Ag—Cu has been used as the solder. However, since Sn—Ag—Cu has a high soldering temperature (equal to or higher than 200° C.), an electronic component having a low degree of heat tolerance is easily damaged. When a substrate formed of PET (polyethylene terephthalate) is used, the substrate is melted at the soldering temperature.
Further, when a coating-film-shaped electrode formed by screen-printing and heating a conductive paste containing metal powder and resin is used, the solder wettability of the electrode is deteriorated, and the resin component of the electrode is thermally decomposed at the soldering temperature.
As described above, when a high-melting-point solder is used, various problems arise. For this reason, it is preferable to use a low melting point solder rather than a high-melting-point solder. However, for example, when an electrode composed of a copper film is used, good environment resistance cannot be obtained. The resistance of the electrode increases due to corrosion. Even when a very small electrode pattern is formed in accordance with a reduction in the size of an electronic component, it is difficult to form a very small electrode pattern with the copper film. Even when it is wanted to use, as the electrode, the conductive coating film formed by screen-printing and heating the conductive paste containing metal powder and resin, the solder wettability of the conductive coating film is low, as described above.
Even when the solder wettability is high, it is required to appropriately reduce the electric resistance between the solder and the electrode.
For example, in JP-A-6-295616, the primary object is to improve the solder wettability of the conductive coating film. However, JP-A-6-295616 does not disclose a technique for improving the solder wettability by using a low melting point solder. JP-A-6-295616 discloses an experiment for testing the solder wettability, but does not clearly disclose which solder is used. In addition, JP-A-6-295616 does not disclose a structure for appropriately reducing the electric resistance between the solder and the electrode. Both JP-A-2004-362950 and JP-A-9-194768 relate to a conductive past. However, JP-A-2004-362950 and JP-A-9-194768 do not disclose the use of a low melting point solder.
As described above, the conventional techniques fail to disclose how to improve the solder wettability of a conductive coating film containing metal powder and resin when a low melting point solder is used, or how to reduce the electric resistance between the solder and the electrode.